1. Field of the Invention
The present invention relates to reclosable plastic bags. This invention more particularly pertains to a fastener tape having reclosable fasteners thereon and adapted to be mounted in an opening of a reclosable bag.
2. Description of the Prior Art
Reclosable plastic bags having interlocking pressure-sealable profile fasteners are well known and have a variety of useful applications, such as the storage of household goods. The recent increase in consumer demand for reclosable bags has been coupled with a demand for higher quality profile fasteners in these bags. To meet these demands, manufacturers must develop cost effective and reliable methods of producing reclosable bags that are suitable for a consumer's particular purpose.
Consumers prefer reclosable bags in which the reclosable opening is across the top of the bag. Until recently, however, most reclosable plastic bags were manufactured with the reclosable opening located along a vertical side of the bag, rather than across the top of the bag. Simply, it was easier for manufacturers using conventional equipment and processes to attach fasteners along the side of the bag than it was to attach fasteners across the top of the bag. Recent advances in manufacturing equipment and materials have allowed some manufacturers to produce reclosable bags with the reclosable openers across the top of the bag. For example, such equipment is available from AMI/Rec-Pro, Inc. in Atlanta, Ga., USA.
Typically, most commercially available reclosable plastic bags are formed of thermoplastic, such as polyethylene. An opening in the plastic bag is equipped with a plastic profile fastener which allows the plastic bag to be opened and resealed when accessing the contents of the plastic bag. These profiles include a male profile and a female profile configured to interlock and form a continuous closure when aligned and pressed together. Interlocked male and female profiles are commonly referred to, in the singular sense, as a profile fastener, zipper profile, or merely as a profile.
There is one type of extrusion process used to extrude materials for use at the top of a bag that is known as a flange zipper process. In such a process, the profile is extruded to form flanged portions, extending from the profile fastener. However, there are problems in sealing extruded, flanged profile directly to the walls of the plastic bag (referred to as the bag walls) due to the thickness of the flanged portions. Specifically, extruded, flanged profile has a limitation as to how thin the flanges can be integrally extruded. The extrusion process results in a flanged area having a thickness significantly greater than if a similar type profile was separately manufactured and attached to a separately manufactured intermediate layer.
As an alternative to attaching flange zipper profiles directly to the bag walls, the profile may only be attached to an intermediate layer of film. The intermediate layer with the attached profile is then attached to the bag walls. The combination of the profile and the intermediate layer is commonly referred to as “fastener tape.” The fastener tape and bag walls are suitably interconnected by generally knows means, such as heat sealing, wherein the intermediate layer is sealed to the walls of the base material. The use of an intermediate layer permits the use of profiles that are made of a different material than the plastic bag walls. These different materials may be thermally incompatible. It is desirable to produce an intermediate layer in the thinnest manner possible in order to minimize the amount of heat necessary to attach the intermediate layer to the plastic bag. The intermediate layer is more effectively attached to a plastic bag with a minimal amount of heat, when the intermediate layer is in its thinnest form.
Excess heat in the manufacture of reclosable plastic bags promulgates defects. For example, if the intermediate layer or the profile comes into contact with excessive heat, the seal between the walls of the plastic bag and the intermediate layer may become damaged or the profile may become deformed. Such damage may be identified by an inoperable profile, wrinkles or creases in the walls of the plastic bag, or curls at the edges of the bag near the profile. Heat sealing is even more difficult when the walls of the bag are something other than polyethylene, for example polypropylene.
When manufacturing reclosable plastic bags with fastener tape, it is often desirable to include a peel seal between opposing portions of the intermediate layer. Such a peel seal assures that the integrity of the bag will be maintained until it is initially opened by the consumer by providing a hermetic seal.
In practice, however, it is has proven problematic to cost-effectively and consistently manufacture fastener tape with a peel seal. Typically in prior art fastener tapes, portions of the intermediate layer are coated with an adhesive. The intermediate layer is then folded so as to bring the adhesive bearing portions into an opposing relationship, after which the adhesive bearing portions are sealed together to form a peel seal. This method, however, is extremely complex and requires exacting control to ensure that the process is kept within acceptable parameters. Additionally, the adhesive tends to hold the ends of the fastener tape together, making the bag difficult to open. Further, it is often difficult to apply the adhesive and the adhesive can be very expensive.
In response to the realized inadequacies of known fastener tapes, it became clear that there is a need for a new type of fastener tape which facilitates the implementation of a peel seal.